Free Practice Quiz Question List

9 Introduction to Modern Physics Online Quiz Questions

Use this free practice quiz with 20 questions to review 9 Introduction to Modern Physics, test your knowledge, and prepare for your next test or exam.

20 questions

True or false

1 point

At short distances inside a nucleus, the strong nuclear interaction binds nucleons together and overcomes the electrical repulsion between protons. True or false?

A
True
B
False

Fill in the blank

1 point

An element is identified by its number of protons, called its .

True or false

1 point

The half-life of a radioactive sample is the time after which every nucleus in the sample has decayed. True or false?

A
True
B
False

Written response

1 point

What is the scientific term for atoms of the same element that have different numbers of neutrons?

Choose one

1 point

For light above a material's photoelectric threshold, its frequency is held fixed while its intensity is increased. What change can the material experience?

A
Each photon becomes more energetic, but the number of emitted electrons stays fixed.
B
More electrons can be ejected, while the energy of each photon stays the same.
C
The photon energy decreases, so fewer electrons are ejected.
D
The work function of the material increases.

Fill in the blank

1 point

In the quantum model of an atom, electron states described by wave functions are often called .

Choose one

1 point

In the simplest hydrogen model, what happens when an electron transitions from $n=2$ to $n=3$ ?

A
The atom absorbs a photon.
B
The atom emits a photon.
C
The electron stays at the same energy because both levels are allowed.
D
The transition cannot occur because hydrogen has only one allowed energy level.

Choose all

1 point

Select all statements consistent with the quantum description of a particle's wave function.

A
The quantity $|\Psi|^2$ gives the probability density for a position measurement.
B
For a normalized wave function, probabilities over all possible positions sum to one.
C
The wave function describes a tiny classical object following a precisely known path.
D
The uncertainty principle is only a limitation of imperfect measuring instruments.

Written response

1 point

A radioactive isotope has decay constant $\lambda=\frac{\ln 2}{8\text{ years}}$ . Using $T_{1/2}=\frac{\ln 2}{\lambda}$ , what is its half-life? Enter the numerical value in years.

Choose all

1 point

Select all correct statements about nuclear binding and nuclear reactions.

A
The mass defect of a nucleus corresponds to binding energy through $E_b=\Delta m c^2$ .
B
Greater binding energy per nucleon generally means a nucleus is more tightly bound.
C
Fission is the joining of light nuclei into a heavier nucleus.
D
Fusion is the splitting of a heavy nucleus into lighter nuclei.

Open ended

1 point

Compare nuclear fission and nuclear fusion. Describe what happens to the nuclei in each process and explain the condition under which the reaction releases energy.

Choose one

1 point

A particle has rest mass $m$ and momentum $p$ . Which relation gives its total relativistic energy $E$ ?

A
$E=pc+mc^2$
B
$E^2=(pc)^2+(mc^2)^2$
C
$E^2=pc+mc^2$
D
$E=(pc)^2+(mc^2)^2$

Choose one

1 point

Light of a fixed frequency shines on a material whose work function is too large for that frequency's photons to eject electrons. What happens if the light intensity is increased without changing its frequency?

A
Each photon has greater energy, so electrons can be ejected even if the frequency is below the threshold.
B
More photons arrive, but each photon still has the same energy.
C
The photons' wavelengths increase, while their energies stay constant.
D
The material's work function decreases as the light gets brighter.

Choose one

1 point

Two neutral atoms have the same number of protons but different numbers of neutrons. How should they be classified?

A
They are different elements because their neutron counts differ.
B
They are ions of the same element because their neutron counts differ.
C
They are isotopes of the same element.
D
They are the same isotope as long as their proton counts match.

True or false

1 point

True or false: The uncertainty relation $\Delta x\,\Delta p\geq\hbar/2$ describes only a limitation caused by imperfect measuring instruments.

A
True
B
False

Choose one

1 point

A particle's normalized wave function is represented by $\Psi$ . Which interpretation of $|\Psi|^2$ is correct?

A
The wave function describes the state, and its squared magnitude gives position probability density.
B
The wave function traces the exact classical path of the particle.
C
The wave function directly gives the particle's momentum at every position.
D
The wave function gives the probability that the particle is at every possible position without further calculation.

Choose one

1 point

A clock measures a proper-time interval of $1.0\text{ s}$ . An observer sees it moving and uses $\gamma=1.67$ . What interval does the observer measure?

A
$0.60\text{ s}$
B
$1.67\text{ s}$
C
$1.0\text{ s}$
D
$2.67\text{ s}$

Choose one

1 point

In a fission reactor, why can neutrons released by one fission event help sustain a chain reaction?

A
The released neutrons combine with electrons to make new atoms.
B
The released photons increase the work function of nearby nuclei.
C
Released neutrons can trigger additional fissions, sustaining a controlled chain reaction.
D
The products fuse with one another, which is what defines fission.

Written response

1 point

Using the simplest hydrogen model $E_n=\frac{-13.6\text{ eV}}{n^2}$ , calculate the energy of the $n=2$ level. Enter the value in eV.

Written response

1 point

What is the nuclear process in which light nuclei combine into a more tightly bound nucleus and release energy?